Components having MEMS elements have been manufactured in mass production for many years for greatly varying applications, for example, in the fields of automotive engineering and consumer electronics. The miniaturization of the components is increasingly gaining in significance. On the one hand, the miniaturization substantially contributes to reducing the manufacturing costs of the components and therefore also of the terminal equipment. On the other hand, in particular in the field of consumer electronics, more and more functions—and therefore components—are to be accommodated in the terminal equipment, while the terminal equipment itself becomes smaller and smaller. Therefore, less and less space is available on the application circuit boards for the individual components.
Various miniaturization concepts for sensor components are known from practice, which provide an integration in one component of the sensor function implemented by micromechanics and the circuitry-wise processing and evaluation of the sensor signals. In addition to the lateral integration of the MEMS function and the ASIC function on a shared chip, there are also already concepts for so-called vertical hybrid integration, according to which a chip stack is formed from ASIC, MEMS, and a cap wafer.
Such a vertically integrated component and a method for the manufacture thereof are described in United States Published Patent Application No. 2011/0049652. The known method provides bonding the starting substrate for the MEMS element on an already processed ASIC substrate. A micromechanical structure, which includes at least one deflectable structural element, is only produced thereafter in the MEMS substrate. Independently thereof, a cap wafer is structured and prepared for the mounting over the micromechanical structure of the MEMS substrate and on the ASIC substrate. The cap wafer thus processed is bonded on the ASIC substrate after the structuring of the MEMS substrate, so that the micromechanical structure is enclosed hermetically sealed between the ASIC substrate and the cap wafer.
The component described in United States Published Patent Application No. 2011/0049652 is equipped with a capacitor system, which—depending on the MEMS function—may be used as a drive for moving the deflectable structural element or also for detecting externally caused deflections of the structural element. For this purpose, the capacitor system includes at least one deflectable electrode, which is located here on the deflectable structural element of the MEMS element, and stationary electrodes, which are implemented here in a structured metal layer on the surface of the ASIC substrate.
The known component concept allows cost-effective mass production of robust components having a micromechanical function and a signal processing circuit, since here not only the individual component parts—MEMS element, cap, and ASIC—are manufactured in the wafer composite, but rather also their assembly is implemented to form a component on the wafer level. The MEMS functions and ASIC functions may be tested on the wafer level, and even the calibration of the individual components may take place before the separation on the wafer level. In addition, the known components require a comparatively small mounting area due to the stacked construction, which has a favorable effect on the manufacturing costs of the terminal equipment.
The positioning of the electrodes of the capacitor system, on the one hand, on the lower side of the MEMS element and, on the other hand, in the uppermost metal level of the ASIC element, has proven to be problematic. Since the capacitance of such a capacitor system is inversely proportional to the distance between the opposing electrodes and the gap between the two elements is generally relatively large, the capacitance of the capacitor system is relatively small here at a given electrode area. The measuring sensitivity is accordingly relatively low if the capacitor system is used for measuring purposes. If the capacitor system is used for activating the movable structural element, a comparatively high voltage must thus be applied to achieve a predefined deflection.
The capacitor system of the known component additionally may not be readily supplemented by a third electrode level for fully differentiated signal detection or activation. It would have to be situated here on the lower side of the cap, i.e., also at a relatively large distance.